JP2013228643A - Method for forming low-reflection film and member with low-reflection film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a porous, low-reflection film with low refraction properties on a substrate, and a member with the low-reflection film.SOLUTION: A low-reflection film-forming coating liquid containing an organotin compound and a hydrolyzate of alkoxysilane is applied to a substrate surface to form a coating film. The organotin compound is contained with respect to the hydrolyzate of alkoxysilane within a range of hydrolyzate of alkoxysilane: organotin compound=99:1-50:50 expressed in terms of a molar ratio by oxide conversion. The method includes to set the coating film to a decomposition temperature or more of the organotin compound. The low-reflection film of a porous oxide film with a refractive index of 1.25 or more and 1.50 or less is formed on the substrate.

Description

  The present invention relates to a method for forming a low-reflection film on a substrate, particularly a transparent substrate, and a member with the low-reflection film. Among the members with a low reflection film obtained by the method for forming a low reflection film according to the present invention, the glass with a low reflection film using a transparent glass as a substrate is used as an automotive glass or a protective member for lighting equipment. Particularly, it is suitably used for a cover glass for a solar cell.

  The low reflection film is a film provided on the substrate surface in order to reduce the surface reflection of the substrate. A transparent substrate such as glass is formed on the surface of the substrate in order to eliminate light loss due to surface reflection and improve the light transmittance (hereinafter sometimes simply referred to as light transmission). The low reflection film is formed not only on the lens surface of optical devices such as still cameras, video cameras, and liquid crystal projectors, but also on general-purpose products such as solar cell cover glass, architectural window glass, showcases, and automotive window glass. It is being done. By forming a low-reflection film on the glass surface, for example, in the cover glass for solar cells, in solar cell output improvement by improving the transmittance of the cover glass, architectural window glass, showcase or automobile window glass, The effect of preventing reflection is obtained.

For example, Patent Document 1 discloses at least one component selected from the group consisting of silica sol (a) having a particle size of 5 to 30 nm, a hydrolyzate of alkoxysilane, a hydrolyzate of metal alkoxide, and a metal salt. (B) and a coating liquid containing 10 to 50 parts by weight of (b) in terms of metal oxide with respect to 100 parts by weight of SiO _{2 in} (a), A low-refractive-index antireflection film obtained by curing after coating is disclosed.

  Patent Document 2 discloses a porous antireflection layer deposition method by a sol-gel method, using a titanium-containing precursor, and adding particles, particularly nanoparticles, to a sol-gel solution. A method for depositing an antireflective layer is disclosed.

  In such a low-reflection film, air having a refractive index of 1 is contained in pores and voids (hereinafter, these may be collectively referred to as voids) inside the film made of silica. A method of lowering the refractive index of the film by forming the film has been tried, and in general, a silica film using a porous silica film or hollow silica fine particles has been studied.

  In addition, a pore is a porous fine hole. The pores are classified into micropores (micropores, micropores, micropores), mesopores (mesopores, mesopores), and macropores (macropores, macropores). In the International Union of Pure and Applied Chemistry (IUPAC), pores with a diameter of 2 nm or less are defined as micropores, pores with a diameter of 2 nm to 50 nm are defined as mesopores, and pores with a diameter of 50 nm or more are defined as macropores.

  A porous silica film is a mesopore or macropore formed in a silica film by applying a raw material liquid that is a mixture of silica sol and a surfactant or a high-boiling-point solvent to a substrate and then forming a film by the sol-gel method. It is obtained by doing. In addition, the sol-gel method means that a sol composed of silicon alkoxide and colloidal silica obtained by dehydrating and condensing it is gelled after being applied to the surface of the body, and then heated and fired to obtain amorphous, polycrystalline, etc. This is a method of forming a relatively hard film.

  The hollow silica fine particles are silica fine particles containing fine voids or mesopores by using an alkoxysilane having a specific alkyl group or the like and aggregating and condensing the same. A film formed on the substrate using these hollow silica fine particles has voids, mesopores, or macropores derived from the hollow silica fine particles, and becomes a low reflection film by the air contained in the voids or mesopores.

  However, the hollow silica fine particles have a problem that the production process is complicated. Therefore, it is difficult to adopt as a cover glass for solar cells, a protective member for lighting equipment, and an automobile glass, which are general-purpose products.

  For example, in Patent Document 3, porous composite oxide particles composed of silica and an inorganic oxide other than silica are coated with a porous silica-based inorganic oxide layer having a thickness of 0.5 nm to 20 nm. A method for producing fine particles having mesopores or macropores is disclosed. By forming a film containing the fine particles on the surface of the substrate, it is said that a substrate with a film having a low refractive index and excellent adhesion to a resin, strength, antireflection ability, etc. can be provided. .

Patent Document 4 includes silica and Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , Ce ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ , MoO ₃ , or WO _3. A composite oxide colloidal sol in which a composite oxide colloidal particle having an average particle size composed of an inorganic oxide other than silica selected in the range of 5 nm to 300 nm is dispersed in water and / or an organic solvent, A composite in which a part of an element other than silica constituting the inorganic oxide is removed and the particle surface is coated with a silica coating, and the refractive index is in the range of 1.36 to 1.44. An oxide sol is disclosed. The composite oxide sol can be used to provide a substrate for low reflection in which a coating film having a low refractive index is formed.

  Patent Document 5 selects from the group consisting of silica fine particles, tungsten oxide, niobium oxide, tantalum oxide, titanium oxide, zirconium oxide, tin oxide, aluminum oxide, hafnium oxide, chromium oxide, cerium oxide, molybdenum oxide and lanthanum oxide. And containing at least one kind of the metal oxide as a binder for the silica fine particles in an amount of 5% by mass to 40% by mass with respect to the silica fine particles, and having a refractive index of 1.20 or more and 1.40 or less. Disclosed are a low reflection film and a method for forming the same.

In the present invention, an organotin compound, in other words, an alkyltin compound refers to a compound in which at least one carbon atom is bonded to a tetravalent tin atom, and four compounds are defined depending on the number of bonds of the organic group R, that is, It is divided into a monoorganotin compound (RSnX ₃ ), a diorganotin compound (R ₂ SnX ₂ ), a triorganotin compound (R ₃ SnX) and a tetraorganotin compound (R ₄ Sn). X is a group bonded by an atom other than carbon, for example, an oxygen atom.

  Among these organotin compounds, the organic group R is a methyl group, n-butyl group or n-octyl group, and one or two organic groups R are bonded to a tin atom, Organotin compounds are mainly used as heat stabilizers for halogen-containing resins such as vinyl chloride resins, and are used in catalysts, glass coating agents, and the like. In addition, it is used as a raw material for polyurethane or a curing agent for silicone rubber. Thus, the main uses of monoorganotin compounds and diorganotin compounds are resin stabilizers, reaction catalysts, and curing agents for resins and paints. Specifically, vinyl chloride resins and chlorinated vinyl chloride resins Or heat stabilization for halogen-containing resins such as chlorinated polyethylene, heat stabilizer for halogen-containing flame retardant-containing resins, catalyst for esterification reaction, catalyst for transesterification reaction, curing agent for polyurethane resin, curing agent for silicone resin and Examples of the curing agent for electrodeposition paints.

  In Japan, about 90% of the organotin compounds are used as heat stabilizers for halogen-containing resins, ie, organotin stabilizers.

    Tetraorganotin compounds are used as raw materials for monoorganotin compounds and diorganotin compounds, but triorganotin compounds are not currently manufactured and used in Japan due to problems of toxicity and environmental impact. Tetraorganotin compounds are very stable and have low toxicity, but can be toxic triorganotin compounds when metabolized. Triorganotin compounds are toxic and have been used as fungicides and insecticides, but in recent years environmental pollution to living organisms has become a problem, and their use is prohibited in Japan. In contrast, monoorganotin compounds and diorganotin compounds have no or low toxicity.

  For example, in Patent Document 6, 100 parts by weight of a silyl group-containing organic polymer (A) having at least one silicon atom bonded to a hydrolyzable group in a molecule terminal or side chain in one molecule and a curing catalyst (B ) A composition comprising 0.1 to 10 parts by weight as a main component, wherein the curing catalyst (B) is a mixture of 80 to 50% by weight of a dialkyltin compound and 20 to 50% by weight of a silicate compound. A moisture curable composition is disclosed.

Patent Document 7 discloses that
_{^{R 1 k-m M (OCOR}} 2) n
(Here, M is a metal atom selected from the group consisting of Sn, Ti, In, Si, Zr, and Al, and R ¹ is a linear, branched, or cyclic group having 1 to 6 carbon atoms. An alkyl group, an alkenyl group, or an aryl group, R ² is an alkyl group having a branched chain having 3 to 6 carbon atoms, k is a number representing the valence of the metal atom M, and m is 1 to k. And a glass coating method in which the coating agent is applied to a glass substrate held at 450 to 750 ° C. to form a metal oxide film on the glass surface. Yes. According to this method, it is said that a film having excellent durability and no haze can be formed on the glass surface.

  The invention described in Patent Document 7 is to obtain a metal oxide film having excellent durability and no haze generation by thermal decomposition of an organic carboxylate, and is intended to improve the wear resistance of glass equipment. . The refractive index of the obtained metal oxide film is 1.7 to 2.2, which is higher than the refractive index 1.52 of soda lime glass, which is a general-purpose glass, and an invention relating to a low reflective film having low refractive index properties is not. Specifically, the organic tin compound itself is thermally decomposed to form a tin oxide film, and the tin oxide film is used for protecting the glass substrate. The tin oxide film is transparent, strong and excellent in chemical resistance, but has a refractive index of 1.8 to 2.0 and does not become a low reflection film having low refractive index properties.

Japanese Patent Laid-Open No. 08-122501 JP 2010-134462 A International Patent Publication No. WO00 / 37359 JP 2006-117526 A International Patent Publication WO / 2012/008427 JP 2001-172515 A JP 2000-119044 A

  There is a need for a glass with a low reflection film that is simple and inexpensive to produce as cover glass for solar cells, architectural glass, showcases, and automobile glass.

  The present invention provides a method for forming a low reflection film for obtaining a porous low refractive index low reflection film on a substrate, particularly a glass plate.

  In the method for forming a low reflection film according to the present invention, a coating liquid for forming a low reflection film containing a sol obtained by hydrolyzing alkoxysilane and an organotin compound is coated and coated on the surface of a substrate to reduce the porosity and the low refractive index. A reflective film is formed. The diorganotin compound is disclosed, for example, in Patent Document 6 as a material for a moisture-curable composition, and in Patent Document 7 as one of metal compounds selected as a glass coating agent. No examples have been used, and there is no report on obtaining a porous low-refractive film on the substrate surface.

  In the present invention, a coating solution for forming a low reflection film containing a sol obtained by hydrolyzing an organotin compound, for example, a diorganotin compound and an alkoxysilane, is applied to and coated on the surface of a substrate such as a glass plate, so that the refractive index is 1. A low-refractive-index low-reflective film made of a porous film containing air in a void is obtained. By using an alkoxysilane and an organic tin compound, the organic tin compound is decomposed in the coating film made of the sol, and a separation gas made of organic gas and water, which is a decomposition product of the organic tin compound such as carbon dioxide, is applied to the coating film. A low-refractive film was generated in which fine voids in which air having a refractive index of 1 was incorporated and tin oxide were dispersed in a film made of silica condensed with the sol. Since the diameter of the void is 50 nm to 150 nm, the light is not dispersed and the transparency of the glass plate is not impaired.

  When the alkoxysilane is baked, the organic component and water generated by the decomposition of the alkoxy group contained in the alkoxysilane do not contribute to the formation of voids. For example, when only tetraethoxysilane (hereinafter sometimes referred to as TEOS) is used, a bulk film without voids is obtained, and a low-flexibility film cannot be obtained.

  Further, when an organic tin compound is added to the film composition, the refractive index is usually increased. However, in the present invention, a porous film having a low refractive index can be obtained for the first time by including an organotin compound and containing an alkoxysilane and an organotin compound together to form a coating film, which is useful as a low reflection film. there were.

  The present invention is as shown in Inventions 1-13.

[Invention 1]
A hydrolyzate of an organotin compound and an alkoxysilane, wherein the organotin compound is expressed in terms of a molar ratio in terms of oxide to the hydrolyzate of the alkoxysilane, and the hydrolyzate of the alkoxysilane: the organotin compound = Refractive index 1.25 including coating the substrate surface with a coating solution for forming a low reflection film contained in a range of 99: 1 to 50:50 to form a coating film that is at or above the decomposition temperature of the organotin compound. A method for forming a low anti-reflection film, comprising forming a low reflective film of a porous oxide film of 1.50 or less on a substrate.

[Invention 2]
The organotin compound is represented by the general formula (1): R ¹ _X SnA _Y (1)
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an alkenyl group or an aryl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. 18 is a linear or branched C3-C18 alkoxy group or alkoxysilyl group, X is an integer of 1 or 2, and Y is an integer represented by 4-X.)
The method of the invention 1 which is a compound represented by these.

[Invention 3]
The organotin compound is represented by the general formula (2): R ¹ ₂ SnA ₂ (2)
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an alkenyl group or an aryl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. 18 linear or branched C1-C18 branched alkoxy group or alkoxysilyl group.) The method according to Invention 1 or Invention 2.

[Invention 4]
The organotin compound is represented by the general formula (3): R ¹ _P Sn (OCOR ² ) _Q (3)
Or general formula (4): R ¹ _P Sn (OCOR ² ) _Q ) O (4)
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an aryl group, or an alkenyl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. 18 is a linear or branched alkoxy group having 3 to 18 carbon atoms or an alkoxysilyl group, p is an integer of 1 or 2, and Q is an integer represented by 4-P or 3-P. )
The method of the invention 1 which is a compound represented by these.

[Invention 5]
The organotin compound is represented by the general formula (5): R ¹ ₂ Sn (OCOR ² ) ₂ (5)
Or general formula (6): (R ¹ ₂ Sn (OCOR ² )) ₂ O (6)
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an aryl group or an aryl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. 18 linear or branched alkoxy group having 3 to 18 carbon atoms or alkoxysilyl group.)
The method of the invention 4, which is a diorganotin compound represented by the formula:

[Invention 6]
Alkoxysilane is represented by the general formula (7): R ³ _m Si (OR ⁴ ) _4-m (7)
(Wherein R ³ and R ⁴ are each independently a linear or branched alkyl group having 1 to 4 carbon atoms, and m is an integer of 0 to 3). The method of invention 1-5 which is a compound or its hydrolyzate.

[Invention 7]
The method of inventions 1-6, wherein the alkoxysilane is tetraalkoxysilane.

[Invention 8]
A member with a low reflection film, wherein a low reflection film is formed by the method of inventions 1-7.

[Invention 9]
The member with a low reflection film of Invention 8 wherein the thickness of the low reflection film is 50 nm or more and 200 nm or less [Invention 10]
The low reflection film member of the invention 8 or the invention 9, wherein a low reflection film having a contact angle of 2 ° or more and 40 ° or less of the surface according to JIS R3257 (1999) is formed.

[Invention 11]
The member with a low reflection film according to inventions 8 to 10, wherein the surface resistance value per 1 cm ³ of the surface on which the low reflection film is formed is 10 ⁶ Ωcm or more and 10 ¹² Ωcm or less.

[Invention 12]
The member with a low reflection film according to inventions 8 to 11, wherein the substrate is a glass plate.

[Invention 13]
The solar cell cover glass which uses the member with the low reflection film of the twelfth invention.

  By the method for forming a low reflection film of the present invention, a porous low reflection film having a low refractive index was formed on a substrate, particularly a glass plate.

  Specifically, it comprises a hydrolyzate of an organotin compound and an alkoxysilane, and the organotin compound is represented by a molar ratio in terms of oxide to the hydrolyzate of the alkoxysilane, and the hydrolyzate of the alkoxysilane: An organic tin compound is decomposed and generated by applying and coating a coating solution for forming a low reflection film included in a range of 99: 1 to 50:50 on the surface of a substrate such as a glass plate. A separation gas composed of a gas and water is generated in a silica film formed by dehydration condensation of alkoxysilane to form a void, and has a low refractive index of 1 as a porous film containing air having a refractive index of 1 in the void. A porous oxide film low reflection film having a thickness of .25 or more and 1.50 or less was formed. The organotin compound is preferably a diorganotin compound.

  When forming a low reflection film on the substrate surface, by applying the alkoxysilane hydrolyzate and organotin compound to the substrate at the same time, the organotin compound decomposes and generates organic gas and water in the film. A member with a low reflective film having a low refractive index film in which fine voids in which air having a refractive index of 1 was taken into a silica film formed by dehydration condensation of alkoxysilane and tin oxide was dispersed was obtained.

2 is a SEM photograph substituting for a drawing of a low reflection film surface of a glass with a low reflection film prepared in Example 1. FIG. It is a graph of the light transmittance of the glass with a low reflection film produced in Examples 1 and 2.

  As described above, the monoorganotin compound and the diorganotin compound used in the method for forming a low reflection film of the present invention are used as a polymerization catalyst for promoting polymerization in the production of a resin, and are stabilizers for vinyl chloride resin. Used as The monoorganotin compound or diorganotin compound added to the silicone resin is intended to act as a curing catalyst, and the one obtained by adding the monoorganotin compound or diorganotin compound to the silicone resin is fired at 400 ° C. or higher. It becomes silica powder and does not form a film.

  In the present invention, by using an alkoxysilane and an organotin compound that give a robust bulk silica film without voids when dehydrated and condensed, not an silica that gives a porous film such as a silicone resin, an alkoxysilane When the silica film is formed by dehydration condensation, the organotin compound is decomposed in the film, and a separation gas composed of organic gas and water, which is a decomposition product of the organic tin compound such as carbon dioxide, is generated in the coating film. A porous low-refractive low-reflective film in which fine voids taking in air having a refractive index of 1 and tin oxide are dispersed in a silica film formed by dehydration condensation of silane is formed.

  That is, the present invention comprises a hydrolyzate of an organotin compound and an alkoxysilane, and the organotin compound is represented by a molar ratio in terms of oxide to the hydrolyzate of the alkoxysilane, thereby hydrolyzing the alkoxysilane. Object: Organotin compound = Applying a coating solution for forming a low reflection film included in a range of 99: 1 to 50:50 on the surface of the substrate to form a coating film, and including setting the organic tin compound to a decomposition temperature or higher This is a method for forming a low anti-reflection film, in which a low reflective film of a porous oxide film having a refractive index of 1.25 or more and 1.50 or less is formed on a substrate.

By making the decomposition temperature of the organotin compound or higher, voids are formed in the silica film in which the hydrolyzate is dehydrated and condensed by the separation gas when the organotin compound becomes tin oxide. In the present invention, liquid stability means that there is no precipitation of an organotin compound or alkoxysilane in the coating liquid for forming a low reflection film, or no gelation of the liquid. In other words, the liquid life is the time until the liquid stability is impaired due to the deterioration of the coating liquid for forming a low reflection film over time. Silica refers to a polymer having a siloxane bond obtained by condensation polymerization of alkoxysilane after hydrolysis. The diameter refers to the maximum diameter of particles or voids.

  Hereinafter, the description will be given in order.

1. Low Reflective Film Forming Coating Liquid The low reflective film forming coating liquid used in the method for forming a low reflective film of the present invention comprises an organotin compound and an alkoxysilane hydrolyzate. The organotin compound is expressed in terms of a molar ratio in terms of oxide, that is, in terms of SiO ₂ or SnO ₂ , hydrolyzate of alkoxysilane: organotin compound = 99: 1 to 50:50 This is a coating solution for forming a low reflection film.

  By applying the coating solution for forming a low-reflection film on the surface of the substrate to form a coating film, and having a decomposition temperature higher than the organotin compound, a low-reflection substrate having a low-reflection film formed on the surface of the substrate can be obtained. . The low reflection film formed using the coating liquid for forming the low reflection film is porous and has a refractive index of 1.25 to 1.50 by taking air having a refractive index of 1 into the void. As a result, the substrate has low surface reflectivity.

  That is, it comprises a hydrolyzate of an organotin compound and an alkoxysilane, and the hydrolyzate of an alkoxysilane: organotin compound = 99: 1 to 50:50 in a molar ratio in terms of oxide. By using a coating solution for forming a low reflection film, and applying it to a substrate to form a coating film, when the alkoxysilane is subjected to condensation polymerization after hydrolysis to form a silica film, by making the decomposition temperature of the organotin compound or higher, A gas composed of an organic gas generated by decomposition of the organotin compound and water is generated to obtain a microvoid. The organotin compound becomes tin oxide after firing. At that time, in the coating solution for forming a low reflection film, the refractive index is 1.25 or more and 1.50 or less by setting the hydrolyzate of alkoxysilane: organotin compound = 99: 1 to 50:50. A porous low reflection film is obtained on the substrate.

  In the coating solution for forming a low reflection film, if the organotin compound is less than a molar ratio of 1, there is no effect of obtaining a porous material, and if it is added more than a molar ratio of 50, a low refractive index cannot be obtained and a low reflective substrate is obtained. Because it is not possible. Preferably, the hydrolyzate of alkoxysilane: organotin compound = 95: 5 to 60:40 or less.

  Hereinafter, the organic tin compound, alkoxysilane, and organic solvent, which are essential components contained in the coating solution for forming a low reflection film used in the method for forming a low reflection film of the present invention, will be described. In addition to these components, a metal alkoxide selected from the group consisting of silicon, zirconium, aluminum and tin for increasing moisture resistance and film hardness, a metal β-diketone or a chelate selected from metal β-diketoesters, An aqueous chelate selected from hydroxyamate, diolate or hydroxyacylate or a carboxylate of these metals may be added.

2. Organotin compound The organotin compound used in the present invention is preferably a monoorganotin compound or a diorganotin compound, excluding triorganotin compounds and tetraorganotin compounds that are toxic and not available. It is preferable to use a commercially available diorganotin compound. Triorganotin compounds and tetraorganotin compounds are difficult to obtain and are not substantially used.

The organotin compound contained in the coating solution for forming a low reflection film used in the method for forming a low reflection film of the present invention includes:
Formula (1): R ¹ _X SnA _Y (1)
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an aryl group, or an alkenyl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. 18 is a linear or branched alkoxy group having 3 to 18 carbon atoms or an alkoxysilyl group, X is an integer of 1 or 2, and Y is an integer represented by 4-X.) Compounds.

In the coating system for forming the low reflection film, it is preferable to use a diorganotin compound because it is commercially available and easily available.
Formula (2): R ¹ ₂ SnA ₂ (2)
(In the formula, R ¹ is a linear alkyl group having 1 to 12 carbon atoms or a branched alkyl group having 3 to 12 carbon atoms, an aryl group, or an aryl group having 6 to 12 carbon atoms, and A is carbon. It is preferable to use a compound represented by a linear or branched alkoxy group having 1 to 18 carbon atoms or an alkoxysilyl group.

After applying the coating solution for forming a low reflection film on the substrate to form a coating film, the organic tin compound is decomposed to generate organic gas or water from these R ¹ and A, which is applied together with the hydrolyzate of alkoxysilane. When this occurs, microvoids are generated in the silica film formed by condensation polymerization of the hydrolyzate.

In the general formula (2), the linear or branched alkyl group having 1 to 12 carbon atoms represented by R ¹ includes a methyl group, an ethyl group, a propyl group, an isopropyl group, and butyl. Group, isobutyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group or lauryl group. Preferably, it is a C1-C8 group. Examples of the linear or branched alkoxy group having 1 to 18 carbon atoms include methoxy group, ethoxy group, propoxy group, butoxy group, isobutoxy group, s-butoxy group, t-butoxy group, pentyloxy group, hexyloxy Group, heptyloxy group, octyloxy group, 2-ethylhexyloxy group, lauryloxy group or stearyloxy group.

  In the present invention, the alkoxy group represented by A is preferably an alkoxy group having 1 to 4 carbon atoms, specifically, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, or an s-butoxy group. , T-butoki and the like. Examples of the alkoxysilyl group include a trialkoxysilicate group, a monoalkyl dialkoxysilicate group, a dialkyl monoalkoxysilicate group, and a trialkylsilicate group.

  Specific examples of the dialkyl tin dialkoxide represented by the general formula (2) include dimethyl tin dimethoxide, dimethyl tin diethoxide, dimethyl tin dipropoxide, dimethyl tin dibutoxide, dimethyl tin bis (2 -Ethylhexyl oxide), dimethyltin dilauryl oxide, dimethyltin distearyl oxide, dibutyltin dimethoxide, dibutyltin diethoxide, dibutyltin dipropoxide, dibutyltin dibutoxide, dibutyltin bis (2-ethylhexyl oxide), dibutyltin dilauryl oxide , Dibutyltin distearyl oxide, dioctyltin dimethoxide, dioctyltin diethoxide, dioctyltin dipropoxide, dioctyltin dibutoxide, di Cutyltin bis (2-ethylhexyl oxide), dioctyltin dilauryl oxide, dioctyltin distearyl oxide, dilauryltin dimethoxide, dilauryltin diethoxide, dilauryltin dipropoxide, dilauryltin dibutoxide, dilauryl Tin bis (2-ethylhexyl oxide), dilauryl tin dilauryl oxide or dilauryl tin distearyl oxide may be mentioned. These dialkyltin dialkoxides can be obtained by heating and reacting a dialkyltin oxide and a corresponding alcohol in a nitrogen atmosphere. Further, it can be obtained by reacting a dialkyltin oxide with an ester compound such as octyl phthalate or ethyl laurate under a nitrogen atmosphere.

  Specific examples of the dialkyltin bis (trialkoxysilicate) represented by the general formula (2) include dimethyltin bis (trimethoxysilicate), dimethyltin bis (triethoxysilicate), and dimethyltin bis (tributoxysilicate). ), Dibutyltin bis (trimethoxysilicate), dibutyltin bis (triethoxysilicate), dibutyltin bis (tributoxysilicate), dioctyltin bis (trimethoxysilicate), dioctyltin bis (triethoxysilicate), dioctyltin bis (tributoxy) Silicate), dilauryltin bis (trimethoxysilicate), dilauryltin bis (triethoxysilicate) or dilauryltin bis (tributoxysilicate).

  Specific examples of the dialkyltin bis (monoalkyl dialkoxysilicate) represented by the general formula (2) include dimethyltin bis (methyldiethoxysilicate), dimethyltin bis (ethyldiethoxysilicate), and dimethyltin bis. (Butyldiethoxysilicate), dibutyltin bis (methyldiethoxysilicate), dibutyltin bis (ethyldiethoxysilicate), dibutyltin bis (butyldiethoxysilicate), dioctyltin bis (methyldiethoxysilicate), dioctyltin bis (ethyldiethoxysilicate) Ethoxy silicate), dioctyl tin bis (butyl diethoxy silicate), dilauryl tin bis (methyl diethoxy silicate), dilauryl tin bis (ethyl diethoxy silicate) or dilauryl tin bis (butyrate) Diethoxy silicate) and the like.

  Specific examples of the dialkyltin bis (dialkylmonoalkoxysilicate) represented by the general formula (2) include dimethyltin bis (dimethylethoxysilicate), dimethyltin bis (diethylethoxysilicate), and dimethyltin bis (dibutylethoxy). Silicate), dibutyltin bis (dimethylethoxysilicate), dibutyltin bis (diethylethoxysilicate), dibutyltin bis (dibutylethoxysilicate), dioctyltin bis (dimethylethoxysilicate), dioctyltin bis (diethylethoxysilicate), dioctyltin bis (dibutyl) Ethoxy silicate), dilauryl tin bis (dimethyl ethoxy silicate), dilauryl tin bis (diethyl ethoxy silicate) or dilauryl tin bis (dibu Le ethoxy silicate) and the like.

  Specific examples of the dialkyl tin bis (trialkyl silicate) represented by the general formula (2) include dimethyl tin bis (trimethyl silicate), dimethyl tin bis (triethyl silicate), dimethyl tin bis (tributyl silicate), and dibutyl tin. Bis (trimethylsilicate), Dibutyltinbis (triethylsilicate), Dibutyltinbis (tributylsilicate), Dioctyltinbis (trimethylsilicate), Dioctyltinbis (triethylsilicate), Dioctyltinbis (tributylsilicate), Dilauryltinbis (trimethyl) Silicate), dilauryl tin bis (triethyl silicate) or dilauryl tin bis (tributyl silicate).

  These dialkyltin silicate compounds can be obtained by heating and reacting dialkyltin oxide or dialkyltin dicarboxylate with a triorganosilicate compound in a nitrogen atmosphere.

In the coating solution for forming a low reflection film used in the method for forming a low reflection film of the present invention, a low reflection film having excellent stability and compatibility with tetraalkoxysilicate, which is a preferred alkoxysilane, low refractive index, and being porous while being porous Than giving
Organotin compounds include general formula (3): R ¹ _P Sn (OCOR ² ) _Q or general formula (4): (R ¹ _P Sn (OCOR ² ) _Q ) O
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an aryl group or an aryl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. 18 is a linear or branched C3-C18 alkoxy group or alkoxysilyl group, P is an integer of 1 or 2, and Q is an integer represented by 4-P or 3-P. It is preferable to use a compound represented by That is, since the valence of Sn is 4, in the general formula (3), Q is 4-P, and in the general formula (4), Q is 3-P.

The tin atom is preferably in the state of 2 organic substituted tin because there is no concern about toxicity and it is easy to obtain, and the coating liquid for forming a low reflection film of the present invention includes:
General formula (5): R ¹ ₂ Sn (OCOR ² ) ₂ or General formula (6): (R ¹ ₂ Sn (OCOR ² )) ₂ O
(R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an aryl group or an aryl group having 6 to 12 carbon atoms, and A is a straight chain having 1 to 18 carbon atoms. It is a linear or branched C3-C18 alkoxy group or alkoxysilyl group.)
It is preferable to use a diorganotin compound represented by:

R ¹ is preferably a methyl group, an ethyl group, a propyl group, a pentyl group, a hexyl group, a lauryl group or an octyl group, and may be a branched isopropyl group, a tertiary butyl group or a 2-ethylhexyl group. Similarly, R ² is preferably a methyl group, an ethyl group, a propyl group, a pentyl group, a hexyl group, a lauryl group or an octyl group, and may be a branched isopropyl group, a tertiary butyl group or a 2-ethylhexyl group. .

As such compounds, dibutyltin dilaurate, ie, (C ₄ H ₉ ) ₂ Sn [OCO (CH ₂ ) ₁₀ CH ₃ ] ₂ , 1,1,3,3-tetrabutyl-1,3-dodecanoyl distanoxane , _{i.e., [(C 4 H 9)} 2 Sn (OCO (CH 2) 10 CH 3)] 2 O, dibutyltin diacetate, _{i.e., (C 4 H 9) 2} Sn (OCOCH 3) 2, dioctyltin dilaurate, That is, (C ₈ H ₁₇ ) ₂ Sn [OCO (CH ₂ ) ₁₀ CH ₃ ] ₂ , dioctyltin diacetate, ie, (C ₈ H ₁₇ ) ₂ Sn (OCOCH ₃ ) ₂ , or dioctyltin dineodecano benzoate, i.e. _{(C 8 H 17) 2 Sn} (OCO (CH 2) 8 CH 3 -neo) 2 can be cited.

  In the coating solution for forming a low reflection film, dibutyltin dilaurate, 1,1,3,3-tetrabutyl-1,3-dodecanoyl distanoxane, dibutyltin diacetate, dioctyltin dilaurate, dioctyl is particularly preferable as the organic tin compound. It is preferable to use at least one selected from the group consisting of tin diacetate and dioctyltin dineodecanoate.

These compounds are available from Nitto Kasei Co., Ltd. under the product name Neostan U-100 (dibutyltin dilaurate, ie (C ₄ H ₉ ) ₂ Sn [OCO (CH ₂ ) ₁₀ CH ₃ ] ₂ ) Neostan U-130 (1,1, 3,3-tetrabutyl-1,3-dodecanoyl distanoxane, ie, [(C ₄ H ₉ ) ₂ Sn (OCO (CH ₂ ) ₁₀ CH ₃ )] ₂ O), neostann U-200 (dibutyltin diacetate , _{i.e., (C 4 H 9) 2} Sn (OCOCH 3) 2), Neostann U-810 (dioctyl tin dilaurate, _{i.e., (C 8 H 17) 2} Sn [OCO (CH 2) 10 CH 3] 2), NEOSTAN U-820 (dioctyl tin diacetate, _{i.e., (C 8 H 17) 2} Sn (OCOCH 3) 2) and Neostan U- As 30 (dioctyltin dineodecanoate, i.e. _{(C 8 H 17) 2 Sn} (OCO (CH 2) 8 CH 3 -neo) 2), commercially available.

3. Alkoxysilane Hydrolyzate of alkoxysilane used in the coating solution for forming a low reflection film used in the method for producing a low reflection film of the present invention,
Formula (7): R ³ _m Si (OR ⁴ ) _4-m (7)
(Wherein R ³ and R ⁴ are each independently a linear alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 or 4 carbon atoms, and m is an integer of 0 to 3).
It is preferable that it is a hydrolyzate of the alkoxysilane represented by these.

In the general formula (7), the linear or branched alkyl group having 1 to 4 carbon atoms represented by R ³ and R ⁴ includes methyl, ethyl, propyl, isopropyl, butyl , Alkyl groups such as isobutyl, s-butyl, t-butyl and the like. The m R ^{3 s} may be the same or different. Further, (4-m) R ^{4 s} may be the same or different.

  Specific examples of the alkoxysilane represented by the general formula (7) and the hydrolyzate thereof include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, and tetrabutoxysilane. And hydrolysates thereof, monoalkyltrialkoxysilanes such as triethoxymethylsilane, triethoxyethylsilane, triethoxypropylsilane, triethoxyisopropylsilane or triethoxybutylsilane, and hydrolysates thereof, dialkyldisilanes Alkoxysilanes such as diethoxydimethylsilane, diethoxydiethylsilane, diethoxydipropylsilane, diethoxydiisopropylsilane or diethoxydibutylsilane, and their additions Hydrolyzate, trialkyl monoalkoxysilanes, for example, triethoxy methyl silane, ethoxy triethylsilane, triethoxy propyl silane, ethoxy triisopropylsilane or ethoxy tributyl silane, and their hydrolysis products thereof. Among these, tetraalkoxysilane or a hydrolyzate thereof is preferable, and specifically, a hydrolyzate of tetraethoxysilane.

4). Organic solvent The organic solvent used in the coating solution for forming the low-reflective film only needs to dissolve or disperse the hydrolyzate of the organotin compound and alkoxysilane, and has a long and stable liquid life among alcohols, esters, and ketones. In addition, it can be selected in consideration of ease of application and safety with respect to a desired application method. Alcohols include mesonol, ethanol, n-propanol, isopropanol, n-butanol or tertiary butanol, esters include methyl acetate, ethyl acetate, propyl acetate or butyl acetate, ketones include acetone, Examples thereof include methyl ethyl ketone and methyl isobutyl ketone, and these may be mixed. In consideration of the alkoxysilane hydrolysis and the safety of the liquid, water may be added to the coating liquid for forming the low reflection film to such an extent that the stability and the liquid life are not impaired.

5. Preparation Method of Low Reflective Film Forming Coating Liquid When preparing the low reflective film forming coating liquid, the aforementioned organotin compound and alkoxysilane hydrolyzate are dissolved in the aforementioned organic solvent or a mixed solvent with water.

  For example, a diorganotin compound is preferably used as the organotin compound, such as dibutyltin dilaurate, 1,1,3,3-tetrabutyl-1,3-dodecanoyl distanoxane, dibutyltin diacetate, dioctyltin dilaurate, dioctyltin. Using diacetate or dioctyltin dineodecanoate, as an alkoxysilane, ethoxytrimethylsilane, ethoxytriethylsilane, ethoxytripropylsilane, ethoxytriisopropylsilane or ethoxytributylsilane, preferably tetraethoxysilane hydrolyzate Used and dissolved in mesonol, ethanol, n-propanol, isopropanol, n-butanol or tertiary butanol.

Concentration of the coating _solution, SiO 2 + SnO ₂ by terms of oxide at 0.2 wt% or more and 20 mass% or less. When the concentration is less than 0.2% by mass, it is difficult to obtain a desired film thickness for the low reflection film. That is, the film is thinner than desired or difficult to form. When the concentration is higher than 20% by mass, it is difficult to obtain a desired film thickness in the low reflection film, and the film becomes thick and cracks are likely to occur. Preferably they are 0.2 mass% or more and 10 mass% or less.

6). Method for Forming Low Reflective Film The method for forming a low reflective film according to the present invention comprises the step of applying the low reflective film-forming coating solution onto the substrate surface to form a coating film, and then decomposing the organic tin compound into tin oxide. In the silica film formed by dehydration condensation of alkoxysilane by generating a separation gas, the coating film is cured while forming voids due to the generation of the separation gas, and the content of tin oxide with respect to silica is 1% by mass or more and 50% by mass. A porous low-reflection film having a refractive index of 1.25 or more and 1.50 or less is formed on the substrate in the following range.

  A major feature of the method for regulating a low reflection film of the present invention is that a low reflection film having a porous low refractive index can be obtained even if it is left in units of days at room temperature. This is presumed to be due to the decomposition of the organotin compound in the process of dehydration condensation of the alkoxysilane.

  By applying the above low reflection forming coating solution on a substrate such as a glass plate, tin oxide and silica are contained, and expressed as a molar ratio of silica: tin oxide = 99: 1 to 50:50. A low reflection film having a refractive index of 1.25 or more and 1.50 or less included in the range is obtained. That is, according to the present invention, a low-reflective film having a refractive index of 1.25 or more and 1.50 or less, which is porous and has air having a refractive index of 1 in a hole (void), was obtained.

Further, since the present low reflection film contains tin oxide, the contact angle is low and becomes 2 ° or more and 40 ° or less, and the surface resistance value of 10 ⁸ Ωcm or more per 1 cm ³ of the surface on which the low reflection film is formed, It was 10 ¹² Ωcm. Silica (SiO ₂ ): tin oxide (SnO ₂ ) in the low reflection film is expressed in terms of a molar ratio, and it is preferable that silica: tin oxide = 99: 1 to 50:50. If the tin oxide is less than 1, there is no effect of obtaining a porous material, and if it is added more than 50, a low refractive index cannot be obtained in the low reflective film, and a low reflective substrate cannot be obtained. More preferably, it is 5 or more and 40 or less.

  In this method, by forming a low reflection film having a film thickness of 70 nm or more and 150 nm or less on both surfaces of the glass plate using the glass plate as a base, the low reflection film having an average transmittance of 95% or more in the light wavelength region of 380 nm to 1200 nm A glass plate with a low reflection film as an attached member was obtained. The thickness of the glass plate is 0.3 mm or more and 1 mm or less for a display, and the solar cell cover glass is 1 mm or more and 6 mm or less.

  The preferable film thickness in the glass plate surface of the low reflection film of the present invention is 50 nm or more and 200 nm or less. If the film thickness is less than 50 nm, the wear resistance is inferior and film formation is difficult. On the other hand, if it is thicker than 200 nm, the film thickness becomes non-uniform and it is difficult to form a film. In order to obtain a low reflectance with respect to visible light, it is preferably 70 nm or more and 150 nm or less, and more preferably 100 nm or more and 120 nm or less.

  The coating liquid for forming the low reflection film is applied to the substrate surface to form a coating film, and then the decomposition temperature of the organotin compound is set to be higher than the decomposition temperature, thereby generating a separation gas when the organotin compound is decomposed to become tin oxide. Then, voids due to generation of separation gas are formed in the silica film formed by baking alkoxysilane to obtain a low reflection film. As described above, the low reflection film can be formed by decomposing the organotin compound. In the method for forming a low reflection film of the present invention, the low reflection film can be formed at room temperature (20 ° C.) for a long time, specifically 24. The low reflection film can also be formed by standing for more than an hour. In order to obtain a hard low-reflection film in a short time, it is preferable to heat and calcinate, and the temperature is appropriately adjusted depending on the material of the substrate, but if it is 900 ° C. or higher, the substrate is deformed and is not realistic. Preferably, it is 800 degrees C or less.

  In the case where the substrate is a plastic transparent substrate, it is preferable to perform the heat treatment at a temperature below which deformation or foaming does not occur depending on the type of substrate.

  In addition, the inorganic glass substrate can be heated and fired at a high temperature of about 700 ° C. by adjusting the heating and baking time. As a preferred embodiment, a low reflection film excellent in abrasion resistance was obtained by heating and baking at 500 ° C. or more and 700 ° C. or less for 2 to 3 minutes, that is, 120 to 180 seconds.

  In order to obtain a member with a low reflection film, a transparent substrate as a substrate for forming a low reflection film comprising the coating liquid for forming a low reflection film of the present invention is made of an organic plastic other than an inorganic glass substrate. A base material etc. can be used. As an example of the inorganic glass substrate, a plate-like material such as soda lime glass, borosilicate glass, aluminosilicate glass, barium borosilicate glass, or quartz glass can be used. Furthermore, these glass substrates include clear glass products, colored glass products such as green bronze, functional glass products such as UV and IR cut glass, low Fe high transmittance glass, tempered glass, semi-tempered glass or laminated glass. Safety glassware can also be used. Further, a pattern such as a template glass may be formed on these glass surfaces.

As ceramics, Si ₃ N ₄ , SiC, sapphire, Si wafer, GaAs, InP, AlN and other substrates are also used.

  Examples of the plastic substrate include polycarbonate (PC), polymethyl mesoacrylate (PMMA), polyethylene terephthalate (PET), triacetyl cellulose (TAC), and polyimide.

  Compared with the prior art (Patent Documents 1 and 2), the low reflection film forming method of the present invention is a composite oxide without removing the inorganic oxide and without covering the surface of the colloidal particles with silica. After preparing the sol, it is possible to directly coat the substrate surface with a single layer film to form a low reflection film without coating the substrate surface.

7). Low reflective film member The base material with a low reflection film having a low knitting film formed on the surface in the method for forming a low reflection film of the present invention is hydrophilic because it has tin oxide, and is antistatic and antifogging. Property and antifouling property.

  By the method for forming a low reflection film of the present invention, a member with a low reflection film having an antistatic property, an antifogging property and an antifouling property was obtained because it has a low refractive index and is hydrophilic and has tin oxide.

  If the member with a low reflection film of the present invention is a glass with a low reflection film, for example, a cover glass for solar cells, an optical material such as a lens, an image display surface such as a cathode ray tube or a liquid crystal display device, a window or a showcase, It can be used in a wide range of fields that require hydrophilicity, antifouling properties, and low antireflection antistatic properties such as plate glass and transparent plastics for skylight materials, water heaters, and lighting fixtures. Specifically, the member with a low reflection film having the low reflection film obtained by the method for forming a low reflection film of the present invention is a cover glass for solar cells, glass for automobiles (particularly windshield) or a protective member for lighting equipment. For example, it can be used to improve the light receiving efficiency of solar cells, improve the conversion efficiency of power generation, prevent the reflection of windshields, or improve the illuminance by high visible light transmittance as a protective member for lighting fixtures, LEDs, organic EL, etc. A special effect is obtained.

  In addition, the member with a low reflection film in which the low reflection film is formed by the method for forming a low reflection film of the present invention can be used as a cover glass for a solar cell if the substrate is a low Fe high-transmittance glass in which Fe content is reduced as much as possible. Useful. When used as a cover glass for solar cells, high transmittance and low reflectance are required, and since solar cells are constantly exposed to sunlight, the material has both antifouling properties, water resistance and weather resistance, etc. Is desired.

  In Examples 1 to 3, glass with a low reflection film was produced by changing the molar ratio of alkoxysilane and diorganotin compound and the type of the diorganotin compound according to the method for forming a low reflection film of the present invention. In Comparative Example 1, a glass with a film using only tetraethoxysilane, and in Comparative Example 2, a glass with a film using only a diorganotin compound was prepared, and the average transmittance, film thickness, refractive index, surface resistance value, contact angle. Was measured.

Table 1 shows the measurement method.

Measurement
Example 1
[Preparation of coating solution for forming low reflection film]
In a 1 liter three-necked flask, 323.3 g of isopropanol was weighed and the inside of the flask was purged with nitrogen. Then, 22.5 g of tetraethoxysilane (hereinafter sometimes referred to as TEOS) was added with stirring, and an additional 30 Stirring continued for a minute. Next, 15.6 g of nitric acid aqueous solution having a concentration of 0.5 mol / liter was gradually dropped into the flask over 1 hour, followed by stirring for 3 hours in a state heated to 50 ° C. to hydrolyze TEOS to obtain a precursor sol. Obtained. Next, after the precursor sol is cooled to room temperature (about 20 ° C., the same applies hereinafter), the alkoxysilane hydrolyzate: organotin compound (SiO ₂ : SnO ₂ ) = 80: 20 in terms of a molar ratio in terms of oxide. Thus, 8.57 g of dibutyltin dilaurate (manufactured by Nitto Kasei Co., Ltd., trade name, U-100) was added and stirred at room temperature for about 2 hours to obtain a colorless and transparent coating solution for forming a low reflection film. When the weight analysis of the heating residue of this coating liquid was conducted, the measurement result was a solid content concentration of 2.20% by mass in terms of oxide (SiO ₂ + SnO ₂ ).

[Formation of low-reflection film]
A soda-lime glass substrate (thickness 3 mm, size 200 mm × 100 mm) is polished with cerium oxide as an abrasive to remove surface deposits, rinsed with pure water, and the surface is dried cleanly. A substrate having one surface masked with a polyethylene sheet was used. After immersing this substrate in a tank filled with a coating solution for forming a low reflection film, the substrate was pulled up at a rate of 3 mm / sec to form a coating film on one side, and then dried in a drying furnace at 100 ° C. Baking was performed at 680 ° C. for 180 seconds. In this way, a glass with a low reflection film having a low reflection film formed on one side was obtained. An SEM photograph of this low reflection film by a scanning electron microscope (SEM) is shown in FIG. As shown in FIG. 1, the low reflection film was a film containing a flat elliptical void of about 30 × 100 nm.

[Evaluation of film properties]
A transmittance curve obtained by the spectrophotometer is shown in FIG.

The soda-lime glass substrate before the formation of the low-reflection film had an average light transmittance (380 to 1200 nm) of 90.2%, whereas the low-reflection film with a low-reflection film formed on one side of Example 1 The average light transmittance of the glass was 94.0%. The film thickness measured by the above measurement method was 112 nm, refractive index 1.32 (635 nm), pure water contact angle 4.0 °, and surface resistance 3.8 × 10 ¹⁰ Ωcm.

Example 2
[Preparation of coating solution for forming low reflection film]
In a 1 liter three-necked flask, 322.8 g of isopropanol was weighed and the inside of the flask was purged with nitrogen. Then, 25.4 g of TEOS was added with stirring, and stirring was continued for another 30 minutes. Next, 17.6 g of nitric acid solution having a concentration of 0.5 mol / liter was gradually dropped into the flask over 1 hour, followed by stirring for 3 hours in a state heated to 50 ° C. to hydrolyze TEOS to obtain a precursor sol. Obtained. Next, the precursor sol was cooled to room temperature, and then dibutyltin dilaurate (Nitto Kasei Co., Ltd.) such that the hydrolyzate of alkoxysilane: organotin compound (SiO ₂ : SnO ₂ ) = 90: 10 in terms of a molar ratio in terms of oxide. 4.28 g (trade name, U-100) manufactured by Co., Ltd. was added and stirred at room temperature for about 2 hours to obtain a colorless and transparent coating solution for forming a low reflection film. When the weight analysis of the heating residue of this coating liquid was conducted, the measurement result was a solid content concentration of 2.20% by mass in terms of oxide (SiO ₂ + SnO ₂ ).

[Formation of low-reflection film]
Subsequently, the glass with a low reflection film was produced in the same procedure as Example 1.

[Evaluation of film properties]
A transmittance curve obtained by the spectrophotometer is shown in FIG.

Example 2 in which a low-reflection film was formed on one side of the soda-lime glass substrate before the formation of the low-reflection film had an average light transmittance (380 to 1200 nm) of 90.2%. The average light transmittance of the glass was 94.1%. The film thickness measured by the measurement method was 103 nm, refractive index 1.29 (635 nm), pure water contact angle 3.5 °, and surface resistance value 3.5 × 10 ¹⁰ Ωcm.

Example 3
In a 1 liter three-necked flask, 322.6 g of isopropanol was weighed and the inside of the flask was purged with nitrogen. Then, 24.0 g of TEOS was added with stirring, and stirring was continued for another 30 minutes. Next, 16.6 g of nitric acid aqueous solution with a concentration of 0.5 mol / liter was gradually dropped into the flask over 1 hour, and then heated to 50 ° C. and stirred for 3 hours in another state to hydrolyze TEOS, thereby precursor sol Got. Next, the precursor sol was cooled to room temperature, and then dioctyltin dineodeca so that the hydrolyzate of alkoxysilane: organotin compound (SiO ₂ : SnO ₂ ) = 85: 15 in terms of a molar ratio in terms of oxide. 6.78 g of Noate (manufactured by Nitto Kasei Co., Ltd., trade name, U-830) was added and stirred at room temperature for 2 hours to obtain a colorless and transparent coating solution for forming a low reflection film. When the weight analysis of the heating residue of this coating liquid was conducted, the measurement result was a solid content concentration of 2.20% by mass in terms of oxide (SiO ₂ + SnO ₂ ).

[Formation of low-reflection film]
Subsequently, the glass with a low reflection film was produced in the same procedure as Example 1.

[Evaluation of film properties]
The soda-lime glass substrate before forming the low-reflection film had an average light transmittance (380 to 1200 nm) of 90.2%, whereas the low-reflection film was formed on one side with the low-reflection film of Example 3. The average light transmittance of the glass was 93.8%. The film thickness measured by the above measuring method was 125 nm, refractive index 1.30 (635 nm), pure water contact angle 3.8 °, and surface resistance value 3.8 × 10 ¹¹ Ωcm.

Comparative Example 1
Only the precursor sol of TEOS prepared in Example 1 was used, no diorganotin compound was added, and only the precursor sol was applied to a soda lime glass substrate in the same procedure as in Example 1. It baked on the conditions of this. The formed film had a refractive index of 1.45 and a film thickness of 108 nm. The transmittance of the obtained glass with a film formed on one side is 91.6%, and the film is a porous film having no low refractive index and no bulk voids, and can be said to be a glass with a low reflection film. It was not a thing.

Comparative Example 2
When only dibutyltin dilaurate (product name, U100, manufactured by Nitto Kasei Co., Ltd.) is added to isopropanol, a liquid is prepared, and a film is formed on a soda lime glass substrate in the same procedure as in Example 1, the glass substrate is cloudy. Only the tin oxide powder was adhered, and a low reflective film could not be formed.

Claims (13)

A hydrolyzate of an organotin compound and an alkoxysilane, wherein the organotin compound is expressed in terms of a molar ratio in terms of oxide to the hydrolyzate of the alkoxysilane, and the hydrolyzate of the alkoxysilane: the organotin compound = Refractive index 1.25 including coating the substrate surface with a coating solution for forming a low reflection film contained in a range of 99: 1 to 50:50 to form a coating film that is at or above the decomposition temperature of the organotin compound. A method for forming a low anti-reflection film, comprising forming a low reflective film of a porous oxide film of 1.50 or less on a substrate. The organotin compound is represented by the general formula (1): R ¹ _X SnA _Y (1)
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an alkenyl group or an aryl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. 18 is a linear or branched C3-C18 alkoxy group or alkoxysilyl group, X is an integer of 1 or 2, and Y is an integer represented by 4-X.)
The method of Claim 1 which is a compound represented by these. The tin compound is represented by the general formula (2): R ¹ ₂ SnA ₂ (2)
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an alkenyl group or an aryl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. The method according to claim 1 or 2, wherein the compound is a diorganotin compound represented by: 18 straight-chain or C3-C18 branched alkoxy group or alkoxysilyl group. The organotin compound is represented by the general formula (3): R ¹ _P Sn (OCOR ² ) _Q (3)
Or general formula (4): (R ¹ _P Sn (OCOR ² ) _Q ) O (4)
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an aryl group, or an alkenyl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. 18 is a linear or branched C3-C18 alkoxy group or alkoxysilyl group, P is an integer of 1 or 2, and Q is an integer represented by 4-P or 3-P. )
The method of Claim 1 which is a compound represented by these. The tin compound is represented by the general formula (5): R ¹ ₂ Sn (OCOR ² ) ₂ (5)
Or general formula (6): (R ¹ ₂ Sn (OCOR ² )) ₂ O (6)
(In the formula, R ¹ is a linear or branched alkyl group having 1 to 12 carbon atoms, an aryl group or an aryl group having 6 to 12 carbon atoms, and A is 1 to 1 carbon atoms. 18 linear or branched alkoxy group having 3 to 18 carbon atoms or alkoxysilyl group.)
The method of Claim 4 which is a diorganotin compound represented by these. Alkoxysilane is represented by the general formula (7): R ³ _m Si (OR ⁴ ) _4-m (7)
(Wherein R ³ and R ⁴ are each independently a linear or branched alkyl group having 1 to 4 carbon atoms, and m is an integer of 0 to 3). The method according to any one of claims 1 to 5, which is a compound or a hydrolyzate thereof. The method according to any one of claims 1 to 6, wherein the alkoxysilane is tetraalkoxysilane. A member with a low reflection film, wherein the low reflection film is formed by the method according to any one of claims 1 to 7. The member with a low reflection film according to claim 8, wherein the thickness of the low reflection film is 50 nm or more and 200 nm or less. The member with a low reflection film according to claim 8 or 9, wherein a low reflection film having a pure water contact angle of 2 ° or more and 40 ° or less according to JIS R3257 (1999) is formed. The member with a low reflection film according to any one of claims 8 to 10, wherein a surface resistance value per 1 cm ³ of the surface on which the low reflection film is formed is 10 ⁶ Ωcm or more and 10 ¹² Ωcm or less. The member with a low reflection film according to claim 8, wherein the substrate is a glass plate. The solar cell cover glass which uses the member with a low reflection film of Claim 12.

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